netdev - Re: [PATCH] Revert "net: linkwatch: add check for netdevice being present to linkwatch_do

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Message-Id: <20200923.172349.872678515629678579.davem@davemloft.net>
Date:   Wed, 23 Sep 2020 17:23:49 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     saeed@...nel.org
Cc:     hkallweit1@...il.com, geert+renesas@...der.be,
        f.fainelli@...il.com, andrew@...n.ch, kuba@...nel.org,
        gaku.inami.xh@...esas.com, yoshihiro.shimoda.uh@...esas.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Revert "net: linkwatch: add check for netdevice being
 present to linkwatch_do_dev"

From: David Miller <davem@...emloft.net>
Date: Wed, 23 Sep 2020 17:21:25 -0700 (PDT)

> If an async code path tests 'present', gets true, and then the RTNL
> holding synchronous code path puts the device into D3hot immediately
> afterwards, the async code path will still continue and access the
> chips registers and fault.

Wait, is the sequence:

	->ndo_stop()
		mark device not present and put into D3hot
		triggers linkwatch event
	  ...
			 ->ndo_get_stats64()

???

Then yeah we might have to clear IFF_UP at the beginning of taking
a netdev down.